1. Field
The disclosure relates to the design of systems utilizing antenna arrays, and more particularly, to an interface between an antenna array and a transceiver.
2. Background
Antenna arrays find application in, e.g., communications systems at radio-frequency (RF) and millimeter-wave frequencies, as well as radar systems. The multiple antenna elements provided in an array are used to compensate for communications link losses and to mitigate the effects of multipath propagation. Typically, an antenna array is coupled to a device, e.g., a radio transceiver integrated circuit (IC), containing active elements for processing the signals transmitted and received over the antenna array.
The physical interface between the antenna array and the active elements may be configured based on the type of antenna elements in the array. For example, a dipole antenna element is typically a balanced structure that includes two differential terminals. A patch antenna, on the other hand, may be an unbalanced structure that includes only one terminal referenced to a ground plane.
To properly connect the antenna elements to the active elements, a balun may be required to perform balanced-to-unbalanced or unbalanced-to-balanced transformation. The balun is usually either placed at the antenna feed, prior to interfacing with the active elements, or directly implemented as an active element. A balun generally introduces undesirable insertion losses into the system. Moreover, a balun implemented as an active element may consume significant power, and its bandwidth is limited by the cut-off frequency of the active devices.
It would be desirable to provide techniques for interfacing an antenna array with active elements that can readily accommodate either balanced or unbalanced antenna structures, without additional insertion losses or significant area requirements.